The Location Management Strategies Computer Science Essay

This paper surveies the jobs related to the location direction schemes, i.e. , Location Area Based, Movement Based, and Timer Based for Wireless webs. The simulation theoretical accounts are based on user gesture and call reaching is based on Poisson arrival procedure. The Timer-based Location Management scheme is one in which the user updates its location sporadically after an interval of clip. This clip is based upon the user ‘s mobility.

The strategy seeks to minimise the mean signaling cost for single Mobile users for both paging and enrollment. In the adaptative Location Area Based scheme, the user updates its location on each Location Area ( LA ) call boundary crossing. In this instance the LA size is adaptative altering harmonizing to the user ‘s mobility features. In the Movement Based Location scheme, the user keeps path of the figure of LA calls boundary and updates when the figure exceeds a predefined value.

Cardinal Wordss: Wireless Networks, Location Management, update/paging

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I. Introduction

Wireless personal communicating webs have besides emerged as an of import field of activity in telecommunications. This rush of involvement is due to several factors such as the increased handiness of wireless personal computer science, amusement and communicating devices, and liberalization of spectrum allotment processs and progresss in digital signal processing and wireless modem engineerings. While these systems have ab initio focused merely on voice and crude package informations applications, it is recognised that they will hold to germinate toward back uping a wider scope of applications affecting picture and multimedia. The increased dependance on networking for concern, diversion and communications, the turning demand for multimedia applications together with a human desire for mobility and freedom from office-only or home-only computer science restraints makes a strong statement for radio integrated webs. Efficient

database and location direction strategies are needed to run into the challenges from high denseness and mobility of users, and assorted service scenarios.

A. Radio Access Protocols

The basic thought in wireless ATM is to supply support for ATM practical connexions ( VC ) with QoS control on an end-to-end footing. Network flat maps are handled with standard ATM cells, which are augmented with a wireless-specific header/trailer on the wireless nexus to back up wireless-specific protocols such as MAC, DLC, and radio control. Standard ATM signalling maps is terminated at the nomadic terminus. Extensions to the ATM signalling protocols have been proposed to manage terminal mobility related maps such as handoff and location direction [ 1 ] . Thus, radio ATM web specifications can be partitioned into two classs: The Radio entree protocols to manage specific maps and Mobile ATM for wireless independent, mobility direction maps.

B. Mobile ATM

Mobile ATM is the term used to denote the set of sweetenings needed to back up terminal mobility within a fixed ATM web. The major maps of nomadic ATM are location direction for function of user names to their current locations, and handoff control for dynamic re-routing of VCs during terminal migration.

C. Routing and QoS Control

Mobile ATM requires extension to bing routing algorithms to cover with path alteration and optimisations associated with handoff. In general, a handoff event may ensue in a important alteration in the optimum path of each active practical circuit associated with the nomadic terminus. Routing in nomadic ATM is closely related to Quality Of Service ( QoS ) control for keeping selected service parametric quantities through the continuance of a nomadic connexion [ 8 ] .

Handover

Handover or Handoff is a basic Mobile web capableness for dynamic support of terminal migration in both wireless ATM and PCS/cellular interconnectedness applications. Realization of this

map requires signaling and web control ( e.g. Public Network to Network Interface ( PNNI ) ) sentence structure extensions for dynamic re-routing of a set of VCs from on wireless port to another. In general, this procedure involves terminal or radio port induction of handoff for several VCs, which may be connected to different fixed or nomadic terminal points. The re-routing mechanism involves path extension from one wireless port to another and/or re-establishing VC subpaths through new ATM

switches or ports [ 1 ] .

D. Location Management

`Location direction is a generic capableness required in webs back uping terminal migration [ 2 ] . This map is required in both the end-to-end radio ATM scenario and PCS/cellular/WLAN backbone scenario ( where the Mobile has a bequest telephone figure, IP or MAC reference ) . Location direction provides a function between a uniq1ue nomadic device

“ name ” and “ routing-id ” which is used to turn up the current end point to which the device is attached. More distributed location direction algorithms which do non needfully necessitate call apparatuss to travel through a place location registry are besides possible, potentially cut downing call constitution hold. An of import execution issue here is the grade to which location services should be integrated with bing ATM name control and routing package. This type of execution offers the advantage of a to the full incorporate connexion control capableness with better public presentation and lower latency than a detached attack.

II. LOCATION MANAGEMANT IN WIRELESS NETORKS

Location direction ( LM ) in radio webs allows the lasting ATM reference of a nomadic terminus ( MT ) to be used in connexion apparatus messages, irrespective of the current location of the MT [ 2 ] . LM does non simply cover with address interlingual rendition, but incorporates characteristics for entree control and privateness, the finding of user ‘s service profile and the enforcement of policies related to accounting and inter-provider roaming.

A. Location Management maps

The LM maps allow the alone designation of the nomadic user and the routing of connexions to a nomadic terminal regardless of its location [ 7 ]

The LM maps involve:

Assignment of alone service identifiers.

Assignment of lasting ATM terminal system reference ( AESA ) for Mobile terminuss.

Location trailing, aids the web in maintaining path of the current lasting -to- impermanent AESA function.

Connection routing.

B. Authentication and Roaming Functions

i‚· Authentication: This map allows the web to verify the individuality of the nomadic user and let the MT to register its location information.

i‚· Rolling support: This map allows a nomadic user to travel from one Mobile ATM web sphere to another, while continuing the ability to originate an terminate ATM connexions.

C. Classification of LM Schemes

All location direction mechanisms developed can be classified in two classs [ 9 ] .

Location Register Scheme, which is used to hive away the location of the nomadic users and this information is used whenever a call has to be delivered to a MT.

Mobile PNNI Scheme, new characteristics are added in the PNNI protocol to accomplish the needed mobility support.

Location Areas

To implement LM, it is necessary to specify location countries, which are radio coverage parts with a common ATM web prefix. An MT within a location country is approachable with a impermanent ATM reference whose web prefix is the same as that of the location country. When the MT moves to a different location country, its impermanent reference alterations and a location update from the MT to the web is required to alter the reference association. The finding of the current location country is a map integrated into the wireless bed. The location country information consists of two Fieldss: a web identifier ( e.g. , ATM web prefix ) and an index.

D. Paging

In cellular systems, a individual location country can dwell of multiple wireless coverage countries ( or cells ) . Since the precise location of the MT within the location country is non known, a broadcast page message must be sent on all cells of a location country to make the MT during call apparatus. The location update process at the End-User Mobility Enabled Switch ( EMAS ) distinguishes between these two instances.

E. Location Update

In the location update control flow, MT sends a location update message to the web when it detects a alteration in location country. This sensing is done in two ways [ 7 ] : During Handover where the MT invokes the Get Candidate Paging Areas ( PA ) and the new location country is conveyed in the Candidate PAs message or When the MT has no unfastened connexion: the demand for handove does non originate. The MT must therefore sporadically raise the Get Candidate PA map to look into if the location has been changed. Once a finding of the alteration in location country is made, the inquiry arises as to how

the MT must direct the location update message to the web. The location update message carries the service identifier, the lasting ATM reference of the MT and the old location country the MT visited. The EMAS-e having the location update message carries out the process given in [ 7 ] to update the location waiter.

F. Mobility Modeling for Individual User

Mobility patterning for an single user requires a theoretical account that describes the time-varying gesture of an person and has gesture parametric quantities readily available for analysis. A basic mobility feature is the addition in user location uncertainness with clip since the last user-network interaction. For our simulation we assume a Brownian gesture with impetus theoretical account for each user for the interest of simpleness [ 3 ] . The unidimensional Brownian gesture with Drift procedure get downing at place x0 at clip t0 can be described as:

2

1

iˆ­

[ xiˆ­x0 iˆ­v ( t iˆ­t0 ) ]

Pb ( x, i?? ) iˆ?

2 D ( t iˆ­t0 )

vitamin E

aˆ¦ . ( 1 )

2i?° D ( t iˆ­t0 )

Where

T i‚? t0 and

Calciferol

is

the

diffusion

changeless

( length2/time ) .It the parametric quantity which represents the location uncertainness of the gesture, and v the impetus speed ( length/time ) which represents the mean speed of a traveling user.

G. Timer Based Update/Paging

Timer based methods as opposed to location-based methods do non necessitate the user to record and procedure location information during the clip between location updates. These consequences in a important decrease in the signaling decrease in the signaling cost involved for turn uping a peculiar user. When an entrance call arrives, the web pages the cells where the user could be located since its last registration/update. Depending on the maximal paging hold allowed, the terminal paging procedure can take topographic point in more than one measure. In each measure, the web selects of the cells for paging. The paging procedure terminates every bit shortly as the Mobile is found. The strategy seeks to minimise the mean signaling cost due to both paging and enrollment for single nomadic users [ 5 ] .

H. Overall Cost of Paging and Registration

The mean overall cost for registration/paging for the optimal timer-based method is calculated as [ 4 ] :

i?¬

1

T

P

iˆ­t

iˆ­t

i?? ( T ) iˆ?

{ i??

2

P

2 ( erf ( T ) iˆ­ 2

(

vitamin E

) iˆ« vitamin E

} ( 2 )

1iˆ­ eiˆ­t

i?°

Where,

T iˆ? i??i?¬p and

P

is

the

paging

cost/signaling message, I? = D/I»p is the mobility index. For simpleness we assume either that I»p = 1 or that I· is measured in cost per mean page interarrival clip, 1/

I»p. Adaptive Location Area Based: The Adaptive Location Area Tracking Scheme proposal [ 3 ] is a strategy, which chooses the LA on a per-user footing. In this strategy, each nomadic performs a location enrollment as it crosses the boundary of its current personal location country and is assigned a new location country. The size and form of the new LA is determined based on the call and mobility features of the user in the old LA. The aim is to minimise the combined mean signaling cost of both paging and enrollment activities for each person mobile user such that the overall system broad signaling cost for location trailing can be minimized.The used theoretical account for user gesture and call reaching is Brownian gesture with impetus procedure and Poisson arrival procedure severally. Under the premise of a unidimensional cellular web environment, the effects of user mobility parametric quantities such as mean motion velocity, location uncertainness and intend call reaching rate on the size and form of single location countries are investigated. The boundaries of the unidimensional LA is given as B1

and B2with B1 i‚? x0 i‚? B2 ; where X0 is the

initial place of the Mobile. The “ Mean First Passage Time ” ( MFPT ) for a Brownian gesture with Drift procedure get downing at X0 is derived in [ 3 ] as:

1 i?¬1iˆ­eiˆ­2v ( x0

iˆ­B1 ) / D

i??

T ( x0, B1, B2 ) iˆ?

i?­

iˆ­2v ( B2

iˆ­B1 ) / D ( B2

iˆ­ B1 ) iˆ­ ( x0

iˆ­ B1 ) i??

( 3 )

V

1iˆ­e

i?®

i??

Cost Structure

The overall signaling cost for paging and enrollment is calculated as [ 48 ] :

i?? iˆ? { Pi?¬

i?¦ B2

iˆ­ B1

i?¶

iˆ«

1

} ( 4 )

P i?§

Lc

i?·

T ( x0, B1, B2 )

i??

i??

Position Optimization of Location Area

Repairing the LA size LLA = B2 – B1, taking derived function of equation ( 4 ) with regard to B1 and puting

di?? / dB1 iˆ? 0 consequences is:

Calciferol

i?¬

Calciferol

iˆ­2v

LLA

Calciferol

B1

iˆ? x0

iˆ«

ln i?­

( 1iˆ­ vitamin E

) } ( 5 )

2v

i?®

2vLLA

III. DESIGNING THE SIMULATOR

The procedure of planing the simulator includes a sequence of processs: ab initio the motion of the user was modeled utilizing the unidimensional Brownian gesture theoretical account with drift procedure [ 6 ] . This mention was used for developing the gesture theoretical account for simulation.The call reaching procedure was assumed to be Poisson with exponential inter-arrival

times. The mean call reaching rate I»p was taken to be 1/60, Diffusion Constant D = 200, and

V =0.For the timer-based scheme, the updates were carried out on two juncture ‘s i.e. , when the inter-arrival clip exceeded the timeout parametric quantity or when the clip between two updates exceeded the timeout interval. The location of the user is besides assumed to be known merely after a call delivery.In the location country based scheme, updates were carried out each clip the user crosses its LA boundary. It is assumed that an update has been made merely before call reaching.

IV.

PERFORMANCE ANALYSIS AND

Consequence

A. Timer Based Location Update/Paging

From equation ( 2 ) for the Overall Cost of

Paging and Registration, i.e. ,

i?¬

1

T

P

2

iˆ­t

iˆ­t

( 6 )

i?? ( T ) iˆ?

1iˆ­ eiˆ­t

{ i??

P

2 ( erf ( T ) iˆ­ 2 (

vitamin E

) iˆ« vitamin E

}

i?°

Figure 1 is plotted for different mobility indices I? , the optimal T is evident for higher mobility indices. The optimal timer value is a map of D and I»p. A higher mobility idex I? requires a shorter update interval T and incurs a higher cost, which clearly indicates that if a user is location volatile and receives calls less frequently, it is better to track the user with smaller t. In contrast, if a user moves less and receives more calls, a longer T is more appropriate.

D as LLA is fixed. For the optimum placement of an LA, the undermentioned consequences are observed. When there is no gesture impetus ( v=0 ) , the LA must be placed symmetrically with regard to the location enrollment reclamation point x0, i.e. , x0 is ever at the centre of the new LA after each enrollment. The LA must be shifted in the way of V and the distance shifted additions with V as shown in figure 2. Diffusion changeless D represents a gesture uncertainness part around the initial place x0. When D is little, the uncertainness part is little. While with big D, there is a larger part, bespeaking that more cells between x0 and B1 that needs to be included in the new LA.Motion with larger V and smaller D suggests more deterministic gesture, while gesture with smaller V and a larger D represents a more random gesture that needs a larger LA to cover.

Fig. 1. The Entire cost versous clip for assorted values of mobility index I? = 100, 500, 1000.

B. Location Area Update/Paging

Based on equation ( 5 ) , figure 2 shows B1 and B2 = B1 + LLA as a map of V for different values of

Fig.2.. Effect of gesture Drift speed and diffusion changeless D on LA placement, presuming LA size = B2 -B1 = 400 and the user initial place x0 =0

V. CONCLUSION

The optimal timer based scheme proves to be the best pick for location updateamong the other scheme. It is besides the simplest to implement since the user merely has to keep a clock to mensurate the clip since its last update and sends an update when the timeout occurs.

The timeout value is set harmonizing to the user ‘s mobility and name arrival features. The optimal timer value T is a map of Diffusion Constant D and name arrival rate I»pA higher mobility index I? requires a shorter update interval T and incurs a higher cost, which clearly indicates that if a user is location volatile and receives calls less frequently, it is better to track the user with a smaller t. In contrast, if a user moves less and receives more calls, a longer T is more appropriate.

The paper besides showed that the timer – based minimal registration/paging cost isdependent on location

unsteadily instead than intend user speed. This is because amobile traveling at a changeless rate an a known way has a mobility index of zerosince there is no uncertainness in its location. Therefore, cost incurred in tracking himdown is minimal.

Diffusion changeless D represents a gesture uncertainness part around the initial place x0. When D is little, the uncertainness part is little. While with big D, there is a big part, bespeaking that more cells between x0 and B1 that needs to be included in the new LA.

Gesture with larger V and smaller D suggests more finding gesture, while gesture with smaller V and larger D represents a more random gesture the demands a larger LA to cover.

VI. Reference

A. Acharya, Jun Li, and Dipankar Raychaudhuri, “ Signing Syntax extensuions for location direction in nomadic ATM ” , ATM Forum/96-1624, Dec. 1996.

D. Raychaudhuri, L. French, R. Siracusa, S. Biswas,

Yuan, and C. Johnston, ” WATMnet: A Prototype

Wireless ATM System for Multimedia

PersonalCommunication ” JSAC particular issue on

Wireless ATM, 95-R-036 ( AP ) . 1995

Z. Lei and Christopher Rose “ Wireless Subscriber

Mobility Management Using Adaptive Individual Location Area for PCS Systems ” , June 1998.

[ 4 ] C. Rose, “ Minimizing the mean cost of paging and enrollment: a timer – based method ” , ACM Wireless Networks 2 ( 2 ) , 1996.

[ 5 ] C. Rose and R. Yates “ Minimizing the mean cost of paging under hold restraints ” , ACM Wireless Networks 1 ( 2 ) : pp 211-219, 1995.

[ 6 ] Sheldon Ross, “ An Introduction to Simulation ”

1987.

file transfer protocol: //ftp.atmforum.com/atm/incoming/Lm3.doc.

J. Ho and I. Akyildiz, “ Local Anchor strategy for

Reducing Location Costss in PCNs, IEEE/ACM minutess in Networking vol. 4, No.5, October 1996.

E. Zervas, A, Kaloxylos, and L. Merakos, “ An

Efficient Location Management Protocol for

Wireless ATM Customer Permises Networks ” ,

1998.